BBB knock sensor - vs egt and O2 sensors

Discussion in 'Wrenchin' Secrets' started by Gary Bohannon, May 25, 2016.

  1. Gary Bohannon

    Gary Bohannon Well-Known Member

    Are there any knock sensors for our old big blocks that are simple and cheap?
    I have that read that they are best for finding the sweet spot in jetting and timing: also obviously safer.
    Max power just at the edge of micro knock.
    Locate at leanest cylinder area (probably #1 with a B4B)
     
    Last edited: May 25, 2016
  2. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    I tried and failed at adapting an early 90's Chevy 350 to my Buick. I think my method for reading it was the weak link. I used a stock GM knock module to read the associated knock sensor but never got any useful data out of the module. MegaSquirt has a knock module add-on I've considered buying a few times and just need to do so at some point to try it out. The module not only will convert the sensor's signal to a usable one but can also filter out valve train noise, which has historically messed with older aftermarket knock sensor setups.

    You can see it just hanging out there. I opened up the drain plug hole, re-threaded it and put the sensor it. It's in the same place as the Chevy 350. Modern LS engine still use the single wire style sensors, but they have two of them, located in the lifter valley. I believe the Grand National utilized a similar sensor but located on the rear of the engine, where the transmission bolts on. The thing I'm unsure of is, I believe these sensors are calibrated/tuned for certain frequencies, which engine use and mounting location can effect. I could be wrong, and maybe in some cases the ECU reading the sensor can scale around what the sensor is tuned for.
    [​IMG]

    I'm thinking of trying one of these two wire bolt on knock sensors on my Firebird engine when I put a turbo on it. I think these ones are more "wide band" on the frequency range.
    [​IMG]


    As for tuning, from people I trust, quite often max power for timing is well short of spark knock. There are exceptions, but most cases a "safe" tune is still the "maximum power" tune. Timing to spark knock and backing off may still be leaving power (and reliability) on the table.
     

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